Receiving system



D. G. M CAA RECEIVING SYSTEM 4 Filed July 29, 1924 INVENTOR. M 9 @6 4, M414 (@2211 ATTORNEY.

- APPARATUS '00., or SYLVANIA.

Ta all whom it may concern:

Be it knownthat I, DAVID G. MCCAA, a citizen of the United States, residing in the city and county of Lancaster, State of Penn-' other natural or artificial disturbances, in-

cluding other radio signals, are reduced or eliminated in a radio orother receiving system, whereby the desired signals are readily distinguishable or become intelligible notwithstanding the simultaneous existence 0 strong disturbing effects. In accordance'with my invention, the received energies representing both the desired signal and the disturbing effect are divided between reactive aths, one of which is employed for eifectmg the translation of the desired signals,.and with another of which is' associated means for impressing thereon a part of the energy of the desired signals previously amplified, to cause a change of reactance, and thereby withholding from the signal-translating path the effects of the undesired oscillations to greater degree than the effects of the signal-representing or desired oscillations. I

My invention resides in the method and apparatus of the character hereinafter 'described and claimed. 3 a This application is in art a division from my appllcation Serial 0. 601,455, filed No vember 17, 1 922.

For an understanding of my method, and for an illustration of some of the forms my apparatus may take, reference is to be had to the accompanying drawing, in which:

Fig. 1 is a diagrammatic view of a receiving system embodying my invention.

Fig. 2 is a diagrammatic view of a modification.

Fig. 3 is a 'fragmenta diagrammatic I view illustrating a modi cation of both Fi land 2.

fileferring to Fig. 1, A represents the anparatus RECEIVING SYSTEM.

Application filed July 29, 1924 Serial No.'728,832'.

ram o. mean, or LANCASTER, rnnnsrnvnn'ra, n'ssreivoca To run ELEornIc' ranxnsnune, PENNSYLVANIA, A conroaarron or runntenna or other absorption structure of a I radio or any other receiving system, connected through the variable inductance L and the primary P of'an oscillation transformer to earth or other counter-capacity E,

the variablecondenser 0 serving to tune the antenna path and the circuit including the primary P to the frequency of the oscillations produced in the antenna system by the energy absorbed from the natural or other mary P is the secondary Sof an oscillation transformer. For tuning the secondary circuit, there is provided the usual tuning condenser 0, whose terminals are connected to the grid circuit of the audion or other vacuum tube detector-amplifier V compris ing the filament or cathode f, grid 9, and

anode or plate a. In the grid path may be.

plate circuit current or a component there-' of to one or more stages of radio or audio frequency amplifying devices, as well understood in the art, the condenser C and theresistance 1- being omitted when the amplification is to occur at radio frequency.

In shunt to the winding T may be connected the condenser C when. thewinding T is that of a telephone or the primary of an audio frequency transformer, the condenser C being omitted in the case where the winding T is the primary of a radio frequency trans Y former, all as well understood in the art.

As thus far described, the receiving apis a usual one and per se is not my invention. t

However, in accordance with my invention, there is connected. in parallel with the primary P, orin anyother divided-or suitably related path or position therewith as regards the antenna circuit or other path traversed by theoscill'ations of the desired signal and the simultaneously existing disturbing effect, a reactance, either capacitative or'inductive, but preferably, as shown, an inductive reactanceL whose amount may be adjustable as indicated; B is'"preferred that the resistance of the inductance L shall be small as compared with its inductance. The magnitude of the inductance 65 medium. Inductively related to the pri- L is preferably so chosen that its reactive effect is great compared with. that of the primary P for oscillations of the-frequency correspondingwith that ofthe desired sig' nal, whereby, if the reactances L and P' only were present, the oscillations representing the desired signal attain a far greater magnitude in the primary P than in the inductance L However, the reactance or inductance L by itself is insufiicient for my purposes, and there is connected in series therewith a variable condenser Ct, which may be conne cted as indicated, and preferably, to the terminals of additional inductance in series with the inductance L this additional series inductance being indicated at L and may be in effect a continuation of the inductance L y and forming therewith in effect an auto-transformer. For a given frequency of the oscillations representing the desired signal, the capacity of the jcon-' denser C may be adjusted to a value with respect to the magnitude of L", I} which causes the reactance of the path If, C, L

in shunt to inductance L for that frequency to vanish or become zero or substantially zero, whereby, under such condition.

and for such time, the efi'ect is the same as if the reactance of inductance l. were reduced to zero because the primary P is en stantially completely robbed of signalrepresenting energy. That is. to say, this effect is the same as if inductance L were short circuited or as if the leads to the two-terminals of the inductance L were vbrought into low resistance conductive contact with each other. The magnitude of the capa'clty of the condenser C vfor this con- 'dition is not that which would be given to the condenser 0* to tune the control circuit L L C by itself or when isolated, to the frequency of the oscillations representing the desired signal, but has been found to be considerably greater, and for long wave lengths, as of the-order of 13,000 meters, is substantially three or four times as great.

7' .In operationof the system, this large de-, sired value. of the ca acity of the condenser 'with whlch is the condenser 0.

C is found by trial y manually adjusting the condenser to produce 0 timum efiect.

As indicated, however, in *ig. 3, it will be understood that the inductance L in the an- 'tenna path may constitute a separate primary of an oscillation transformer whose secondar is the inductance L m circuit In all the arrangements shown herein there is coupled to the inductance L a coil D traversed'by the amplified currents innthe plate c1rcu1t of a thermionic amplifier V,

.whose gridcircuit includes the condenser C and inductance'S, for tuning that circuit tothe frequenciyhof the received or desired 0sclllatlons. e winding S is the secondary ofan oscillation transformer whose primary l? is included in the branch with the primary P, Fig. 1, or, as indicated in Fig. 2, is located directly in the antenna path in series with both branches therein.

The coil D is preferably rotatable or niovable-with respect to the coil L for adjusting the amplitude of theoscillations of desired or signal frequency impressed by the coil D upon the control path or circuit compris ing the inductance L and condenser C, and associated cooperative parts. When the primary P is traversed by feeble signal-representing oscillations it inductively affects the grid -circuit of the amplifierW, through the coupling P, S there by inturn causing an amplified signal-rep resenting oscillation to inductively affect the The oscillatlonsimpressed the coil D 7 upon the control circuit or path are of the same frequency as those of the desired signal, and the circuit arrangement described Silcircuit or path containing the condenser C is of a character .utilizable for reception of sound waves, including s eech, music, etc, or is utilizable in genera for purposesof telephony.

When the coilD is impressin oscillations upon the control circuit or pat there obtains such strength in such patlor circuit as to in effect open it, havin the e ect of increasing thereaetance in s nut to the primar .Pj, accordingly forcing more. of the rece-ived signal energy through the primary By the arrangement described, and as described in my aforesaid application, the effects of-the relatively stronger static and other disturbances upon the'signal-translating circuit are substantially relatively smaller than theefi'ects thereon of the de-v sired signal oscillations. The system is such" that the ratio of the effect upon the signalt-ranslating'circuit of the desired received oscillations to-the effect upon the same circuit of the stronger static oscillations is far greater than the ratio of the received signal oscillations to the static oscillations as present in the antenna pathwithout recource to my invention.-

While in the foregoing description currents of radio frequency have been assumed and considered, it will be understood that my invention is not limited thereto, but in its broader aspect comprises a method of and apparatus for differentiating between currents, whether'of audio or radio frequency, which maybe of the same frequency but of different amplitudes; -or comprises a method.

of and apparatus for reducing the diflerence between eflects of such audio or radioxfrequeniiy currents, whereby the, weaker may produce a desired effect of greater relatlve magnitude than otherwise possible.

What claim is: 1. The method of distinguishing between radio frequency oscillations representing a desired signal and oscillations represent ing a disturbing eflect, which comprisessubjecting .to the influence of both sets of oscillations a signal-translating circuit and a control pathincludin'g inductive and capa'citative reactances, selectin in a circuit tuned to the frequency of SflId oscillations representing the desired signal 'a portion of thejenergy thereof, amplifyingsaid selected energy, and ,-impressing selected amplified energy upon said control. path for varying its reactance for withholding to differ-- e'nt degrees from said signal-translating circuit the efijects of both said setsof oscillations. g f v 2. Radio receiving apparatus for distinguishing between oscillations ofradio frequency representing a desired signal and oscillatipns representing a disturbing effect, comprising signal-translating means influenced byboth sets of oscillation, a control path including capacitative and inductive reactances and so disposed that changes in the reactance of said path cause said sets of oscillations to influence said signal-translating means to 'difl'erent degrees, means for amplifying a portion of the energy of the oscillations representing the desired signal, and means for impresslng energy so ampl1- .fied upon said control path to Vary its"re-. actance. v 3.1Radior iving apparatus for'distin- 'guishi ng between oscillations of radio frequency representing a desired signal and 0s 'cillat-ions representing adisturbing efi'ect,

coniprising signLaLtranslating means influenced by bothsets of oscillation, a control path including capacitative and inductive 4; The method of distinguishing between fluctuating currents of different amplitudes,

which comprises impressing the currents upon a current-translating circuit and upon a control path upon the magnitude of whose reactance depends the magnitude of effect in said translating circuit, amplifying energy of one of said currents, and imprmsing the amplified energy on the control path for changing said reactance for withholding from said translating circuit the efl'ect of "another of said currents to greater degree than the effect of said one of'said currents. 5. Radio receiving apparatus for distinguishing between oscillations of radio frequency representing a desired signal and 0scillations representing a disturbing eflect,

comprising signal-translating means influenced by both sets'of oscillations, a reactive control path so'disposed that changes in the reactance of said pathcause said sets of oscillations to influence said signal-translating means to difl'erent degrees, means for am-' plifying a portion of the energy'of the oscillations representing the desired signal, and means for impressing energy so amplified upon 'said ance.

control path to vary its react-' DAVE) G. MoCAA. 

